Lithium found to be a superconductor

Theorists may have to go back to the blackboard to explain what happens to compressed lithium under high pressure and low temperature conditions. Experiments have now transformed this lightest metallic element into a superconductor under pressures consistent with theory, but with temperatures that are much lower than predicted. The results, reported in the October 17, Science, suggest that similar theories on superconductivity in solids should be reexamined. Lead author of the study, Viktor Struzhkin of the Carnegie Institution of Washington's Geophysical Laboratory noted, "As a student I was taught that alkali metals (e.g., lithium and sodium) are completely understood within the existing condensed matter concepts. But recent findings inspired by the latest theoretical advances are showing complicated phenomena that were unanticipated."

Superconductivity occurs when a material is cooled to a specific low temperature, which eliminates all electrical resistance allowing the electrons to flow freely. Researchers from Carnegie, and the Max Planck Institut für Chemie, in Mainz, Germany, in addition to a high school intern from the Thomas Wootton school in Rockville, Maryland, subjected the element to pressures of 23 to 80 gigapascals, ( 200,000 to 800,000 times the atmospheric pressure at sea level) and temperatures of 9 K to 16 K (about -444?F to -430?F)--a critical temperature that is among the highest thus far discovered for an element. These conditions led to the superconducting state.

Lithium is difficult to work with in these kinds of experiments because it is highly reactive and hard to contain under the extreme conditions. For the first time using a combination of techniques, the scientists were able to measure both the electrical resistance and the magnetic properties of the element. It appears that there are multiple transitions in the structure of the compressed material. Pressure as a variable is unfolding as a new phenomena in condensed matter. This finding would not be possible without continued advances and innovations in high-pressure techniques. The new data add to the recent body of information about lithium, which has led to a reevaluation of the element. It appears that seemingly simple metals may not be so simple after all. "These experiments provide theorists with a new critical benchmark for understanding dense matter," Struzhkin concludes.

Researchers on this project include Viktor Struzhkin, , Ho-kwang Mao and Russell Hemley from the Geophysical Lab of the Carnegie Institution of Washington; Mikhail Eremets from Max Planck; and Wei Gan, intern at Carnegie and student at Thomas Wootton High School.

The Carnegie Institution of Washington (www.CarnegieInstitution.org) has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments in the U.S.: Plant Biology, Global Ecology, The Observatories, Embryology, the Department of Terrestrial Magnetism, and the Geophysical Laboratory.

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